When looking for your textbooks, check first online at
www.bigwords.com
I love it. It searches the used and new book sites (you can specify which you prefer) and finds the best deals. I always called ahead, or visited campus early, to get my book list and then bought them online. Make the judgement about whether it's worth it to get them shipped or pay a few bucks more in the bookstore.
Think about which books you may want to use later. My intro Bio/Chem books got shelved but my 400 level Psychology books stayed with me. Sell back what you don't want but do think about keeping some.